Dynamic Planet

Ablation

The loss of ice and snow from a glacier system through processes like melting, runoff, sublimation, evaporation, calving, and wind transportation.

Ablation Moraine/Ablation Till

An irregular-shaped layer or pile of glacier sediment formed by melting stagnant ice, deposited on the former bed of the glacier.

Accumulation

The addition of ice and snow into a glacier system through processes like precipitation, firnification, and wind transportation of snow.

Accumulation Area / Névé

The part of a glacier that is perennially covered with snow.

Advance

An increase in the length of a glacier when less ice is lost due to melting or calving than the amount of yearly advance.

Arete

A jagged, narrow ridge that separates two adjacent glacier valleys or cirques, resembling the blade of a serrated knife.

Barren Zone

An area of fresh, vegetation-free bedrock around the margin of a retreating glacier.

Bergschrund

A large crevasse that develops at the head of a glacier where ice pulls away from the bedrock wall.

Bergy Seltzer/Ice Sizzle

The crackling or sizzling sound made as air bubbles released during the melting of glacier ice.

Braided Stream (Anastomizing Stream)

A stream characterized by a network of branches that continuously separate and reunite, common with a high sediment load.

Calving

The process by which pieces of ice break away from the terminus of a glacier.

Chatter Marks

Small, closely spaced grooves formed in bedrock by rocks frozen in basal ice as they move along.

Cirque

A bowl-shaped depression eroded into the head or side of a glacier valley.

Crescentic Gouge

Curved marks produced by plucking or chipping of the glacier's bed.

Crevasse

A crack in the surface of a moving glacier caused by differential stresses.

Debris Cone

A mound of debris-covered ice, with a thick enough sediment cover to protect the ice.

Dendrochronology

The study of tree rings and subfossil wood to provide information about glacial and climatic history.

Disarticulation

The process in which large blocks of ice detach from the terminus of a glacier.

Distributary

A tongue of glacier ice that flows away from the main trunk of a glacier.

Downwasting/Thinning

The thinning of a glacier due to melting of ice.

Drift

A term for all types of glacier sedimentary deposits, regardless of size or sorting.

Drumlin

An elongated ridge of glacial sediment sculpted by moving ice.

Erratic

A rock transported a significant distance by a glacier and deposited by melting.

Esker

A meandering, water-deposited, generally steep-sided sediment ridge formed within a subglacial stream.

Eustacy

Fluctuations in worldwide sea-level due to changes in seawater quantity.

Firn

An intermediate stage in the transformation of snow to glacier ice that is compressed.

Firn line

A line that marks the transition between exposed glacier ice and the snow-covered surface.

Fjord

A glacially eroded or modified U-shaped valley extending below sea level.

Foliation

The layering that develops in a glacier during the transformation of snow to glacier ice.

Fountain

A glacial spring discharging supercooled water.

Glacial Groove/Glacial Furrow

A linear depression produced by the erosive action of a glacier.

Glacial Lake

An accumulation of standing liquid water on, in, or under a glacier.

Glacial Stream

A channelized accumulation of water on, in, or under a glacier.

Glacier

A large, perennial accumulation of ice, snow, rock, and water moving down slope under gravity.

Glacier Cave

A cave formed in or under a glacier, typically by running water.

Glacier Flow

The movement of ice in a glacier caused by the force of gravity.

Glacier Ice

A mono-mineralic type of rock formed through the metamorphism of snowflakes.

Glacier Table

A rock balanced on ice, elevating it above the glacier's surface.

Hanging Valley

A former tributary glacier valley incised into the upper part of a U-shaped glacier valley.

Holocene

The current part of geologic time that began ~12,000 years ago.

Horn

A pointed mountain peak bounded by the walls of three or more cirques.

Ice Rafting

The transportation of glacier sediment away from the ice margin by icebergs.

Ice Shelf

The floating terminus of a glacier formed when a glacier flows into a deep water basin.

Iceberg

A block of ice that has calved from a glacier and is floating in water.

Ice-Dammed Lake

A lake restricted from flowing by an ice dam.

Icefall

Part of a glacier where ice flows over a steep gradient, resulting in fractures.

Ice-Marginal Lake

A lake located adjacent to a glacier's terminus.

Isostasy

The balance of Earth's crust and mantle changes in response to mass changes.

Jökulhlaup

A glacier outburst flood resulting from the failure of a glacier-ice dam.

Kame

A sand and gravel deposit formed by running water on glacier ice.

Kettle

A depression formed by the melting of glacier ice that was buried by sediment.

Little Ice Age (Neoglaciation)

The recent interval of temperate glacier expansion that began ~650 years ago.

Mass Balance

A measure of change in glacier mass due to accumulation and ablation.

Moraine

Unstratified and unsorted sediment deposits formed by glacier action.

Moulin (Glacier Mill)

A tubular chute through which water enters a glacier.

Nunatak

A mountain peak that protrudes through the surface of an ice field or glacier.

Ogive

An arcuate band formed on a glacier's surface at the base of an icefall.

Outwash plain

A low-slope angle alluvial plain composed of transported glacial sediment.

Pit Pond

A depression in an outwash plain formed by melting ice buried by sediment.

Pleistocene

The epoch known as 'The Great Ice Age', lasting from ~1.8 million to ~8,000 years ago.

Plucking

Mechanical removal of rock pieces from a bedrock face by glacier ice.

Remnant

An isolated melting mass of glacier ice detached from its source.

Retreat

A decrease in the length of a glacier due to loss of ice at the terminus.

Roche Moutonnee

A rounded bedrock knob produced by glacier erosion.

Rockslide

Landslides generated by seismic activity that fell onto a glacier.

Rock Flour

Fine-grained sediment formed by glacier erosion of bedrock.

Sérac

A jagged pinnacle of glacier ice located on its surface.

Snowbridge

A mass of snow that masks the existence of an open crevasse.

Stagnation

The in-situ melting of glacier ice.

Striations

Parallel grooves carved into bedrock by rocks frozen in a glacier.

Suncups

Bowl-like depressions melted into a snow or ice surface.

Surge

A large-scale increase in the movement rate of ice within a glacier.

Tarn

A lake that develops in the basin of a cirque after a glacier melts.

Terminus

The lower-most margin or extremity of a glacier.

Till

An unsorted and unstratified accumulation of glacial sediment deposited directly by a glacier.

Trimline

A boundary line on a glacier valley indicating the maximum recent thickness of the glacier.

U-Shaped Valley

A valley formed by glacier erosion, characterized by steep sides and a flat floor.

Varve

A pair of sedimentary layers formed in an annual cycle in a glacial lake.